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At the time of writing, this is how the `TopicPosterSerializer` looks like: ``` class TopicPosterSerializer < ApplicationSerializer attributes :extras, :description has_one :user, serializer: PosterSerializer has_one :primary_group, serializer: PrimaryGroupSerializer has_one :flair_group, serializer: FlairGroupSerializer end ``` Within `PosterSerializer`, the `primary_group` and `flair_group` association is requested on the `user` object. However, the associations have not been loaded on the `user` object at this point leading to the N+1 queries problem. One may wonder why the associations have not been loaded when the `TopicPosterSerializer` has `has_one :primary_group` and `has_one :flair_group`. It turns out that `TopicPoster` is just a struct containing the `user`, `primary_group` and `flair_group` objects. The `primary_group` and `flair_group` ActiveRecord objects are loaded seperately in `UserLookup` and not preloaded when querying for the users. This is done for performance reason so that we are able to load the `primary_group` and `flair_group` records in a single query without duplication.